Oxygen Sensor Heating

FUNCTION
The O2 sensor heater relay is no longer used. The heating of the four O2 sensors is now controlled through final stages, directly by the respective DME control modules.

With a cold engine the DME control modules are programmed to gradually increase the duty cycle of the heater circuits to ground based on time and engine temperature. This function is a preventative for thermal shock of the sensor.

MONITORING
The direct control of the heating elements enables the control modules to also monitor the heating elements and circuits for shorts and opens. These advancements are for compliance with the EPA requirement set forth in OBD II.